Patent Application
20100143111
This application claims priority under 35 U.S.C. ยง119 to European Patent Application No. 08170848.9 filed in Europe on Dec. 5, 2008, the entire content of which is hereby incorporated by reference in its entirety.
The disclosure relates to the field of exhaust-gas-driven turbochargers, which, for example, include a compressor having a circulation chamber which is delimited from a main flow.
To increase the power of an internal combustion engine, it is known to use exhaust-gas turbochargers having a turbine in the exhaust section of the internal combustion engine and having a compressor which is positioned upstream of the internal combustion engine. Here, the exhaust gases of the internal combustion engine are expanded in the turbine. The work which is gained here is transmitted by a shaft to the compressor which compresses the air supplied to the internal combustion engine. By using the energy of the exhaust gases to compress the air supplied to the combustion process in the internal combustion engine, it is possible to optimize the combustion process and the efficiency of the internal combustion engine.
DE 42 13 047 A1 discloses an exhaust-gas turbocharger, in the housing of which a compressor wheel rotates. The housing has an inlet duct into which is inserted an inner wall which firstly forms the main duct contour and secondly delimits an annular circulation chamber which surrounds the main duct. The interior space of the annular chamber is connected to the compressor inlet by an opening and, in the region of the compressor wheel, to the inlet duct by an annular slot in the contoured wall of the annular chamber. The contoured wall is held concentrically with respect to the housing by webs.
The annular chamber which is provided in compressors of this type is a so-called characteristic-map-stabilizing measure. Here, before the compressor surge limit is reached, a recirculation of the flow from the compressor wheel back into the inlet duct upstream of the compressor wheel may take place, as a result of which the compressor wheel experiences an apparently higher throughput. In the operating range close to the compressor choke limit, the annular slot is utilized by the flow as an additional inlet. Recirculation therefore no longer takes place, which results in the desired displacement of the surge limit toward higher throughputs.
The desired expansion of the characteristic map of the compressor often comes at the expense not only of efficiency losses but also of the generation of inadmissible noise and vibrations. Such vibration excitations in the rotor blades may be attributed inter alia to the support ribs which serve to fasten the inner wall of the annular chamber to the housing.
Various noise-reducing measures have been proposed. For example, EP0605184B1 discloses a compressor in which the generation of noise is supposed to be reduced by virtue of a multiplicity of ribs, which are offset relative to one another, being provided in the annular chamber or upstream of the annular chamber with respect to the flow direction of the air, which ribs deflect and partially reflect the sound, thereby reducing the noise. The attachment and arrangement of the ribs is however relatively complex and only partially successful, since the sound is nevertheless transmitted to the compressor housing and radiated into the environment.
A compressor of an exhaust-gas turbocharger is disclosed, comprising: a rotatably mounted compressor wheel; a main flow duct for supplying a medium for compression to the compressor wheel; and a circulation chamber, arranged radially outside the main flow duct and delimited from the main flow duct by a contoured wall, which extends from an intake region of the main flow duct to a circulation opening formed into the contoured wall in a region of rotor blades of the compressor wheel, with the contoured wall being fastened to a housing of the compressor by struts in the circulation chamber, wherein a spacing between struts in at least one pair of struts arranged adjacent to one another in the circulation chamber is different in a circumferential direction than a spacing between struts arranged adjacent to one another in other pairs of struts.
An exhaust-gas turbocharger is disclosed having a compressor which comprises: a rotatably mounted compressor wheel; a main flow duct for supplying a medium for compression to the compressor wheel; and a circulation chamber, arranged radially outside the main flow duct and delimited from the main flow duct by a contoured wall, which extends from an intake region of the main flow duct to a circulation opening formed into the contoured wall in a region of rotor blades of the compressor wheel, with the contoured wall being fastened to a housing of the compressor by struts in the circulation chamber, wherein a spacing between struts in at least one pair of struts arranged adjacent to one another in the circulation chamber is different in a circumferential direction than a spacing between struts arranged adjacent to one another in other pairs of struts.
Exemplary embodiments of a compressor according to the disclosure are schematically illustrated and explained in more detail below on the basis of the figures. In all the figures, equivalent elements are provided with the same reference numerals. In the figures:
Vibration-reducing measures are disclosed for a compressor having a circulation chamber which is delimited from the main flow.
According to the exemplary embodiments, the struts which support a contoured wall are arranged spaced apart from one another to different extents in a circumferential direction.
A uniform distribution of support ribs can lead to formation of exemplary excitation orders in the vibration excitation, with the excitation orders being directly dependent on the number of support ribs. With a non-uniform distribution, the available excitation energy can be distributed between different excitation orders. The excitation per excitation order can therefore be reduced, and specific resonances can be targeted and avoided (e.g., suppressed). A non-uniform distribution of the support ribs can therefore lead to a reduced excitation of the rotor blade vibration.
The non-uniform distribution of the support ribs can have an effect on distribution of the circumferential stiffness. In general, the compressor housing which receives the flow of the radial compressor stage downstream of the diffuser and supplies the flow to the pipeline system can be configured as a spiral, and therefore need not be circumferentially symmetrical. This can lead to a non-uniform deformation in operation as a result of thermal loading of the housing. As a result, a non-uniform distribution of degrees of play between a rotating compressor and a stationary housing can be formed. To prevent the rotor blades of the compressor wheel from grinding against the housing parts, the mean play can be increased, which can lead directly to efficiency losses. With non-uniform distribution of the support ribs, the inner housing which is close to the flow duct is also provided with a non-uniform stiffness over the circumference. A combination of the inner and outer housings can enable a reduction in play and provide an increase in efficiency.
Optionally, all of the pairs of struts arranged adjacent to one another can have a different spacing than the other pairs of struts arranged adjacent to one another.
A circulation chamber which is configured according to the exemplary embodiments disclosed herein can be used in a compressor with a swirl-generating inlet guide wheel. Here, the inlet guide wheel is arranged upstream of the intake region of the main flow duct with respect to the flow direction and, upstream of the compressor inlet, positively imparts a positive or negative flow component in the circumferential direction to the air which is supplied to the compressor.
An exemplary compressor of an exhaust-gas turbocharger is illustrated in
An annular circulation chamber 13 is arranged in an interior of the compressor housing, which circulation chamber 13 radially surrounds the main flow duct and extends from the intake region 11 to an at least partially encircling circulation opening 12 in the region of the guide blades of the compressor wheel 1. The circulation chamber 13 is open in the direction of the main flow duct via two openings. A radial inlet opening is arranged upstream of the compressor wheel, and a radial contoured groove, the circulation opening 12, is arranged downstream of a leading edge of the compressor wheel and in a region of overlap with the inlet thereof. Between the encircling circulation openings, the circulation chamber 13 is delimited from the main flow duct by an annular contoured wall 15. The contoured wall is connected to the inner compressor housing by means of a plurality of struts 14.
According to the disclosure, the struts which support the contoured wall can be spaced apart from one another to different extents in the circumferential direction, as illustrated in
In one exemplary embodiment, all of the pairs of struts arranged adjacent to one another have a different spacing than the other pairs of struts arranged adjacent to one another.
The struts 14 which support the contoured wall may be configured with blade profiles or guide webs, of any desired shape, in order to impart a desired swirl to the flow in the circulation chamber.
The struts 14 can all be aligned purely radially or can all be inclined to the same extent or different extents relative to the radial direction.
The circulation opening 12 can be formed as an encircling annular gap or can be divided into a plurality of annular gap segments. Likewise, the annular chamber can be divided into a plurality of segments in the circumferential direction. Here, the segments can be of equal size or of different sizes.
Thus, it will be appreciated by those skilled in the art that the present invention can be embodied in other specific forms without departing from the spirit or essential characteristics thereof. The presently disclosed embodiments are therefore considered in all respects to be illustrative and not restricted. The scope of the invention is indicated by the appended claims rather than the foregoing description and all changes that come within the meaning and range and equivalence thereof are intended to be embraced therein.
| Number | Date | Country | Kind |
|---|---|---|---|
| 08170848.9 | Dec 2008 | EP | regional |
